1. Field of the Invention
The present invention relates to a temperature control method for a refrigerator, which is constituted to distribute a common refrigerant to a plurality of chambers for cooling each chamber.
2. Description of Related Art
In a valve device which distributes a common refrigerant to a plurality of chambers for cooling the respective chambers in a refrigerator, as shown in FIG. 5 (A), in general, an inflow port (not shown), where the refrigerant flows into, and a first outflow port 13a and a second outflow port 13b, where the refrigerant flows out, are positioned in a sealed space. The two planar valve elements 30a and 30b are arranged in the same sealed space. The two planar valve elements 30a and 30b are respectively formed with gears 36a and 36b in an integral manner, and a pinion 17a integrally rotating with the rotor of a stepping motor is engaged with the respective gears 36a and 36b. 
Therefore, when the stepping motor is driven, the rotation of the motor is transmitted to the valve elements 30a and 30b through the pinion 17a and the gears 36a and 36b. Here, a mode where the first outflow port 13a is in a closed state and the second outflow port 13b is in a closed state is referred to as a CLOSE-CLOSE mode, a mode where the first outflow port 13a is in a closed state and the second outflow port 13b is in an open state is referred to as a CLOSE-OPEN mode, a mode where both of the first outflow port 13a and the second outflow port 13b are in an open state is referred to as an OPEN-OPEN mode, and a mode where the first outflow port 13a is in an open state and the second outflow port 13b is in a closed state is referred to as an OPEN-CLOSE mode. By means of controlling angular positions of the valve elements 30a and 30b, HOME position in a CLOSE-CLOSE state shown in FIG. 5(A), the CLOSE-CLOSE mode shown in FIG. 5(B), the CLOSE-OPEN mode shown in FIG. 5 (C), the OPEN-OPEN mode shown in FIG. 5(D), the OPEN-CLOSE mode shown in FIG. 5(E), and a stop position in an OPEN-CLOSE state shown in FIG. 5(F) are respectively obtained in this order.
In the conventional refrigerator, after a power source is turned on, it is controlled that the OPEN-OPEN mode is set for supplying a refrigerant from the first outflow port 13a to a first chamber and from the second outflow port 13b to a second chamber. After the first chamber and the second chamber have been cooled to a prescribed temperature, the respective temperatures in the first chamber and the second chamber are independently controlled in accordance with the mode to be selected.
However, in the conventional refrigerator, when the power source is turned on, the first chamber and the second chamber are cooled by setting in the OPEN-OPEN mode. In this case, there is a problem that cooling rates are often largely different from each other in the first and the second chambers as shown in FIG. 4(B). In the drawing, temperature changes in the first chamber and the second chamber are respectively shown as the lines of L11 and L12. Consequently, when foods are stored in a cold state or in a frozen state, there is a problem that the temperature difference in the first chamber or the second chamber becomes large, which causes dispersion in quality.
To prevent the above-mentioned problem, a countermeasure has been adopted in which the diameters of the first outflow port 13a and the second outflow port 13b are formed in the same dimension with high precision. However, the cooling rates in the first chamber and the second chamber do not become the same.
The reason may be that, even when the diameters of the first outflow port 13a and the second outflow port 13b have the same dimension, the mounting posture of the refrigerant distributing device to the refrigerator, or the like, causes the flow rate of the refrigerant vary. In other words, when a fluorocarbon or an alternative fluorocarbon is used, 95% or more of the refrigerant, which flows in from the inflow port, changes into gas due to a tube expansion-or the like, while the liquid spreads on a wall surface from the inflow port to the outflow port on a wall surface from the inflow port to the outflow port. Therefore, the variation of the distance from the inflow port to the outflow port or the variation of the position of the outflow port causes to vary the flow amount of the refrigerant.
Consequently, an experimental result was obtained that, after a power source has been turned on, for example, even when the cooling rate in a first chamber is higher than that in a second chamber, the cooling rate in the second chamber can become higher as shown in FIG. 4(B) by changing the posture of the refrigerant distribution device. Furthermore, the mounting posture of a valve device is generally different for every refrigerator manufactured. Therefore, it is extremely difficult to produce a balance of the cooling rates in every refrigerator.